JP6325772B2 - Imaging lens and imaging apparatus having the same - Google Patents

Description

  The present invention relates to an imaging apparatus, and is an imaging apparatus having an imaging lens that forms a subject image on an imaging element such as a CCD sensor or a CMOS sensor, and is suitable for a monitoring camera, a network camera, an in-vehicle camera, a digital camera, and the like. The present invention relates to an imaging device having a simple imaging lens.

  Conventionally, surveillance cameras are required to be small and light, to have a wide imaging range, and to be compatible with low illuminance. In recent years, the number of pixels in the sensor has been increased, and a high resolution for FULL HD is required. Accordingly, an imaging lens mounted on a surveillance camera is required to be small and light, have a wide field angle of 75 degrees or more, a bright F number, and high optical performance. Patent Document 1 proposes a low-cost and compact optical system having good optical performance and a maximum field angle of about 85 degrees. Patent Document 2 proposes an optical system having a good field of view with a maximum field angle of 70 to 80 degrees, an F number of 2.0, and six lens elements.

Japanese Laid-Open Patent Publication No. 2005-221920 JP 2008-233610 A

  In general, in an imaging lens for monitoring, it is preferable that chromatic aberration is corrected well in order to obtain good imaging performance.

  In general, surveillance cameras are used in a wide temperature range from cold regions to tropical regions. For this reason, in a so-called pan focus lens that does not have a focus mechanism in particular, when the imaging position changes due to temperature, the range in which the depth of field is in focus (that is, the pan focus range) changes. It is important that the change in the imaging position is suppressed. In Patent Document 1, since a plastic aspherical lens having a large refractive index change due to temperature is used in order to obtain a small optical size and good optical performance at a low cost, there is a problem that a change in imaging position due to temperature occurs.

  In Patent Document 2, the second-order spectrum of axial chromatic aberration cannot be satisfactorily corrected with the glass material configuration of the third lens group that contributes to image formation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging lens that is small and lightweight, has a wide angle of view, a bright F-number and chromatic aberration are well corrected, has high optical performance, and suppresses changes in the imaging position due to temperature. It is providing the imaging device which has.

An imaging apparatus according to the present invention is a single-focus imaging lens including a first lens group, an aperture stop, and a second lens group having a positive refractive power, which are arranged in order from the object side to the image side. 1 lens group, disposed in order from the object side to the image side, a negative meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface on the object side, and a positive lens, the second The two lens group includes a negative lens and two or more positive lenses, the refractive index based on the d-line of the material of the lens included in the second lens group is N2a, the Abbe number is ν2a, the partial dispersion ratio is θ2a, When the amount of change in the refractive index with respect to the temperature change in the d-line is dn2a / dT, the second lens group is
62 <ν2a
N2a <1.63
0.605− (ν2a / 1000) <θ2a
dn2a / dT <−2.4 × 10 ⁻⁶
A positive lens that satisfies the conditional expression
F is the focal length of the entire system, f2a is the focal length when there is one positive lens that satisfies all the conditional expressions included in the second lens group, and f2a when there are two or more positive lenses. When the total length of the photographing lens is TD and the back focus of the photographing lens is BF,
0.20 <f / f2a <0.80
3.00 <TD / BF <6.50
Satisfying the conditional expression
When the focal length of the first lens group f1, the refractive index relative to the d line of the material of said positive lens in the first lens group and N1P,
-0.21 <f / f1 <0.25
1.88 <n1p <2.40
The following conditional expression is satisfied.

  Further objects and other features of the present invention will be made clear by the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, an imaging lens and an imaging apparatus that are small and light, have a wide angle of view, a bright F-number, and chromatic aberration are favorably corrected to achieve high optical performance and a focal position shift due to temperature change is well corrected. It is done.

Lens sectional view of Numerical Example 1 Aberration diagram at the object distance of 1 m in Numerical Example 1. Lens sectional view of Numerical Example 2 Aberration diagram at the object distance of 1 m in Numerical Example 2. Lens sectional view of Numerical Example 3 Aberration diagram at object distance 1 m in Numerical Example 3 Lens sectional view of Numerical Example 4 Aberration diagram at object distance 1 m in Numerical Example 4 Lens sectional view of Numerical Example 5 Aberration diagram at object distance 1 m in Numerical Example 5 Schematic diagram of main parts of an imaging apparatus of the present invention

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a lens cross-sectional view of an imaging lens of Example 1 (Numerical Example 1) of the present invention. The imaging lens according to the present exemplary embodiment includes, in order from the object side, a first lens group G1, an aperture stop SP, and a second lens group G2 having a positive refractive power. The first lens group G1 includes, in order from the object side, negative meniscus lenses L1 and L2 and a positive lens L3 that are convex on the object side. FL is a parallel plate corresponding to a low-pass filter, an IR cut filter, or the like. I is an imaging surface, which corresponds to an imaging surface such as a solid-state imaging device (photoelectric conversion device) that receives subject light and performs photoelectric conversion.

  FIG. 2 is an aberration diagram of the numerical example 1 at an object distance of 1 m, and the unit is mm (distortion only%). In the longitudinal aberration diagram, spherical aberration indicates e-line (solid line) and g-line (two-dot chain line). Astigmatism indicates the sagittal image plane (solid line) and the meridional image plane (dotted line) of the e-line. The lateral chromatic aberration is represented by the g-line (two-dot chain line). Fno represents an F number, and ω represents a shooting half angle of view. In the longitudinal aberration diagram, the spherical aberration is drawn on a scale of 0.1 mm, the astigmatism is 0.1 mm, the distortion is 10%, and the lateral chromatic aberration is drawn on a scale of 0.02 mm. In the lateral aberration diagram, sagittal ray aberration (solid line) and meridional ray aberration (dotted line) of e-line are shown and drawn on a scale of 0.02 mm. The notation and scale of the aberration diagrams are the same in the following examples.

An imaging lens of the present invention and an imaging apparatus having the same are configured by a first lens group having a positive or negative refractive power, a stop, and a second lens group having a positive refractive power in order from the object side. The second lens group includes a 2a lens group that includes at least one positive lens, and the refractive index of all lenses included in the 2a lens group at the d-line is N2a, and the Abbe number is ν2a. When the partial dispersion ratio is θ2a and the relative refractive index change due to temperature at the d-line is dn2a / d T ,
62 <ν2a
N2a <1.63
0.605− (ν2a / 1000) <θ2a
dn2a / d T <−2.4 × 10 ⁻⁶
The focal length of the entire system is f, the focal length of the 2a lens group is f2a, the total length of the imaging lens is TD, and the image side surface of the lens arranged closest to the image side of the imaging lens When the distance from the imaging surface to the imaging surface is BF, the following conditional expression is satisfied.
0.20 <f / f2a <0.80 (1)
3.00 <TD / BF <6.50 (2)

  Here, both the correction of the chromatic aberration and the suppression of the change in the imaging position due to the temperature change, which are the features of the present invention, will be described.

First, a correction method for chromatic aberration will be described from the viewpoint of chromatic aberration correction conditions in a thin contact system and correction of a secondary spectrum. Chromatic aberration correction conditions for thin-walled adhesive systems

ここで、Ｎｄ、ＮＦ、Ｎｃはフラウンフォーファ線のｄ線（５８７．６ｎｍ）、Ｆ線（４８６．１ｎｍ）、Ｃ線（６５６．３ｎｍ）における屈折率を表している。 Here, φ is the power of the lens and is defined as the reciprocal of the focal length. The subscript i indicates the number of each lens. ν is an Abbe number and can be expressed by the following equation.

Here, Nd, NF, and Nc represent refractive indexes of d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of Fraunhofer lines.

Since the second lens group as a whole has a strong positive refractive power, in order to satisfy the chromatic aberration correction condition of formula (a), the positive lens has a large Abbe number optical material, that is, a low dispersion material, a negative It is necessary to use an optical material having a small Abbe number, that is, a high dispersion material for the lens.
Next, attention will be focused on the chromatic aberration correction condition for the g-line (435.8 nm), which has a shorter wavelength than the F-line, so-called secondary spectrum. Here, when the partial dispersion ratio regarding the g-line and the F-line is θgF, it can be expressed by the following equation.

  Existing optical materials have a tendency that the partial dispersion ratio θgF is larger as the Abbe number is smaller than the Abbe number νd, and the partial dispersion ratio θgF is smaller as the Abbe number is larger.

  In the second lens group, an optical material having a small Abbe number is used for the negative lens in order to satisfy the chromatic aberration correction condition for the two colors of F-line and C-line, so the partial dispersion ratio θgF of the negative lens has a large value. . Therefore, the refractive index of the g-line becomes higher from the equation (c), and the imaging position of the g-line remains in the image side direction (hereinafter referred to as “over”), which becomes the secondary spectrum remaining amount. Therefore, it is possible to correct the residual secondary spectrum by using an anomalous dispersion material having a large partial dispersion ratio θgF even if the Abbe number is large in the positive lens.

  From the viewpoint of aberration theory, the axial chromatic aberration is proportional to the square of the object paraxial ray height hi, and the magnification chromatic aberration is proportional to the product of the object paraxial ray height hi and the pupil paraxial ray height hbi. Both axial chromatic aberration and lateral chromatic aberration are proportional to the refractive power φi of each lens. Therefore, it is possible to satisfactorily correct the secondary spectrum by applying the anomalous dispersion material to a lens having a high paraxial ray height and strong refractive power.

As the definition of the anomalous dispersion material in the present invention, all of the following conditions shall be satisfied.
62 <νd (d)
Nd <1.63 (e)
0.605− (νd / 1000) <θgF (f)
dn / d T <−2.4 × 10 ⁻⁶ (g)
In the formula (g), dn / d T represents a change in relative refractive index due to temperature at the d-line. The relative refractive index change is defined by the temperature change of the refractive index in air at the same temperature as the optical material. In general, the anomalous dispersion material has a negative relative refractive index change dn / d T due to temperature.

Next, a change in the imaging position accompanying a temperature change will be described.
There are mainly two factors that are dominant in the change of the imaging position accompanying the temperature change. The first is a change in the refractive index of the optical material accompanying a temperature change, and the second is a change in the lens interval due to the expansion and contraction of the lens barrel.

First, the refractive index change of the optical material accompanying the temperature change will be described.
The change in imaging position dskGi / dn due to the refractive index change in an arbitrary lens can be expressed by the following equation using the object paraxial ray height hi, the refractive power φi of the lens, and the refractive index Ni of the lens. The subscript i indicates each lens number.

From the formula (h), in the case of a positive lens, the change in the imaging position due to the change in refractive index changes to the object side (hereinafter expressed as “under”), and in the case of a negative lens, it changes to over. Also, the higher the object paraxial ray height hi, the stronger the refractive power φi of the lens, and the lower the lens refractive index Ni, the greater the change in imaging position dskGi / dn due to the refractive index change. The change dskG / dT of the imaging position due to the change in the refractive index of the optical material accompanying the change in temperature can be expressed by the following equation.

  When the anomalous dispersion material is applied to a lens having a high object paraxial ray height and a strong refractive power in order to satisfactorily correct the secondary spectrum of longitudinal chromatic aberration from the equation (i), the change in the imaging position with the temperature change. dskG / dT has a large value over.

Next, the change in the imaging position due to the temperature expansion and contraction of the lens barrel will be described.
The change dskM / dT of the imaging position due to the expansion and contraction of the lens barrel accompanying the temperature change can be expressed by the following equation.

  Here, αi is a linear expansion coefficient of the material of the lens barrel member, Di is a lens interval, and dski / dD is a change in the imaging position due to a change in the lens interval. The subscript i indicates the number of each lens interval. When the lens barrel expands due to a temperature rise and the arbitrary lens interval regulated by the lens barrel member increases, the object point position of the lens group arranged on the image side becomes farther than that interval, so the imaging position must be It becomes under. Also, when the distance from the image side surface of the lens arranged closest to the image side of the imaging lens group to the imaging surface (hereinafter referred to as back focus) increases due to the expansion of the barrel member, the imaging position is under Become. As described above, the change dskM / dT of the imaging position due to the expansion and contraction of the lens barrel accompanying the temperature change is also under.

となる。（ｋ）式より異常分散材料の使用により、温度上昇に伴いオーバーとなる結像位置の変化を、鏡筒部材の材質を適切に選ぶことによりアンダーに補正し、結果として温度による結像位置の変化を抑制することが可能となる。 From (i) and (j), the change in imaging position due to temperature is

It becomes. From the equation (k), the use of an anomalous dispersion material corrects the change in the imaging position that becomes over with a rise in temperature to the under by appropriately selecting the material of the lens barrel member. It becomes possible to suppress the change.

  In particular, the back focus requires a wide interval because a low-pass filter, an IR cut filter, and the like are arranged, and the interval change is equivalent to the change of the imaging position (that is, dsk / dD = −1). Since this is a dominant factor in the change of the imaging position due to the temperature expansion and contraction of the lens barrel, it is necessary to appropriately select the material of the lens barrel member that restricts the back focus.

Conditional expression (1) regulates the ratio of the focal length of group 2a to the focal length of the entire system, thereby suppressing the change in the imaging position due to the temperature change while favorably correcting the secondary spectrum of axial chromatic aberration. The conditions for doing so are specified. If the upper limit of the expression (1) is exceeded, the refractive power of the second group a becomes too strong, and the change of the imaging position accompanying the temperature rise becomes excessively excessive. When the lower limit of the expression (1) is exceeded, the refractive power of the second group a becomes too weak, and the secondary spectrum of the longitudinal chromatic aberration is insufficiently corrected. Furthermore, it is preferable to set the equation (1) as follows.
0.30 <f / f2a <0.68 (1-a)

Conditional expression (2) defines the condition for suppressing the change in the imaging position due to temperature by defining the ratio of the back focus to the total length of the imaging lens. If the upper limit of the expression (2) is exceeded, the back focus with respect to the entire length of the imaging lens becomes too short, and it becomes difficult to arrange an optical filter such as a low-pass filter or an IR cut filter. When the lower limit of the expression (2) is exceeded, the back focus with respect to the entire length of the imaging lens becomes too long, and the change in the imaging position due to the expansion accompanying the temperature rise of the lens barrel member that restricts the back focus becomes excessively under. Further, the increase in the back focus increases the size of the imaging device. Furthermore, it is preferable to set the equation (2) as follows.
3.80 <TD / BF <5.50 (2-a)

The image pickup lens of the present invention and the image pickup apparatus having the same satisfy the following conditions when the maximum image height of the image pickup element is Y and the F number in an infinite state is Fno.
0.40 <f ² /(Y×Fno)<3.00 (unit: mm) (3)

Conditional expression (3) defines the hyperfocal distance, that is, the closest distance, by defining the focal length of the entire system, the maximum image height of the image sensor, and the F number in an infinite state. The hyperfocal distance sh can be expressed by the following equation where ε is an allowable circle of confusion.
sh = f ² / (ε × Fno) (unit: mm) (1)

Furthermore, ε is proportional to the pixel pitch p of the image sensor I. Further, when the pixel pitch p is the number of pixels n in the diagonal direction of the image sensor,
p = 2 × Y / n (m)
Can be expressed as Therefore, the hyperfocal distance sh can be replaced by the following expression from (l) and (m).
sh∝f ² / (Y × Fno) (unit: mm) (n)

If the upper limit of the expression ( 3 ) is exceeded, the focal length of the entire system becomes too long and widening cannot be achieved. If the lower limit of the expression ( 3 ) is exceeded, the focal length of the entire system becomes too short, and it becomes difficult to correct various aberrations including distortion. In addition, the hyperfocal distance becomes long, and the subject distance range in focus is narrowed. Furthermore, it is preferable to set the equation (3) as follows.
0.64 <f ² /(Y×Fno)<2.40 (unit: mm) (3-a)

The imaging lens of the present invention and the imaging apparatus having the imaging lens satisfy the following conditions, where α is the linear expansion coefficient of the material of the lens barrel member that restricts the back focus.
1.50 × 10 ⁻⁵ <α <2.50 × 10 ⁻⁵ (4)

  Conditional expression (4) defines a condition for suppressing a change in the imaging position due to temperature by defining a linear expansion coefficient of the material of the lens barrel member that regulates the back focus. If a material that exceeds the upper limit of the expression (4) is selected as the lens barrel member that restricts the back focus, the imaging position due to the temperature rise will be excessively under. If a material that exceeds the lower limit of equation (4) is selected as the lens barrel member that restricts back focus, the change in the imaging position due to the change in the refractive index of the anomalous dispersion material accompanying a rise in temperature cannot be suppressed, resulting in a result. The image position is over.

The imaging lens of the present invention satisfies the following conditions when the focal length of the second lens group is f2, and the average values of Abbe numbers of the positive lens and negative lens of the second lens group are ν2p and ν2n, respectively.
0.20 <f / f2 <0.70 (5)
2.00 <ν2p / ν2n <6.00 (6)

Conditional expression (5) defines conditions for achieving a wide angle of view and high performance by defining the ratio of the focal length of the second lens group to the focal length of the entire system. If the upper limit of the expression (5) is exceeded, the refractive power of the second lens group becomes too strong, making it difficult to correct various aberrations. If the lower limit of the formula (5) is exceeded, the refractive power becomes too weak, and it becomes difficult to obtain a wide angle of view sufficient for monitoring purposes. Furthermore, it is preferable to set the equation (5) as follows.
0.30 <f / f2 <0.50 (5-a)

Conditional expression (6) defines conditions for achieving suppression of chromatic aberration and various aberrations by defining the ratio of the Abbe numbers of the positive lens and negative lens of the second lens group. If the upper limit of the expression (6) is exceeded, the longitudinal chromatic aberration is overcorrected. If the lower limit of the expression (6) is exceeded, the individual lens refractive power in the second lens group becomes too large, and various aberrations increase, making it difficult to obtain high optical performance. Furthermore, it is preferable to set the equation (6) as follows.
2.80 <ν2p / ν2n <5.30 (6-a)

In the imaging lens of the present invention, the second lens group includes a cemented lens of a negative lens and a positive lens, and satisfies the following conditional expression when the refractive indexes of the negative lens and the positive lens of the cemented lens are ncn and ncp. Is preferred.
0.20 <ncn−ncp <0.60 (7)

The cemented lens has a configuration that effectively corrects chromatic aberration, but by increasing the refractive index difference between the positive lens and the negative lens constituting the cemented lens in the second lens group, the reference wavelength (d line) on the cemented surface is increased. ) Can be increased, and not only chromatic aberration but also spherical aberration and coma can be corrected. When the upper limit of the expression (7) is exceeded, the Abbe number ratio becomes too large in the existing lens material, and the axial chromatic aberration is overcorrected. When the lower limit of the expression (7) is exceeded, the refractive power of the cemented surface becomes too small, and the aberration correction effect on the cemented surface cannot be obtained. Furthermore, it is preferable to set the equation (7) as follows.
0.33 <ncn-ncp <0.57 (7-a)

In the imaging lens of the present invention, the focal length of the first lens group is f1, the average values of the Abbe numbers of the positive lens and negative lens of the first lens group are ν1p and ν1n, respectively, and the d-line of the positive lens of the first lens group. When the refractive index is n1p, it is preferable to satisfy the following conditions.
-0.25 <f / f1 <0.25 (8)
0.20 <ν1p / ν1n <0.70 (9)
1.85 <n1p <2.40 (10)

Conditional expression (8) defines the ratio between the focal length of the entire system and the focal length of the first lens unit. If the upper limit of the expression (8) is exceeded, the convergence of the light beam incident on the second lens group becomes too large, and it becomes difficult to achieve sufficient back focus. If the lower limit of the expression (8) is exceeded, the divergence of the light beam incident on the second lens group becomes too large, and it becomes difficult to correct various aberrations. More preferably, the equation (8) is set as follows.
-0.21 <f / f1 <0.12 (8-a)

Conditional expression (9) defines the ratio of the average values of the Abbe numbers of the positive lens and the negative lens in the first lens group. If the upper limit of equation (9) is exceeded, axial chromatic aberration will be overcorrected. If the lower limit of the equation (9) is exceeded, the longitudinal chromatic aberration is insufficiently corrected. More preferably, the formula (9) is set as follows.
0.25 <ν1p / ν1n <0.63 (9-a)

Conditional expression (10) defines the refractive index at the d-line of the positive lens in the first lens group. By suppressing the occurrence of negative distortion in the first negative lens and the second negative lens, and generating positive distortion in the positive lens of the first lens group, it is possible to more effectively reduce the negative distortion. Yes. In order to generate a positive distortion, it is necessary to refract off-axis rays greatly, which causes higher-order halo and coma aberration in the peripheral image height. In order to suppress the occurrence of these higher-order aberrations, it is effective to increase the refractive index n1p and weaken the refractive power of the positive lens. If the upper limit of the expression (10) is exceeded, the Abbe number becomes too small with the existing lens material, the axial chromatic aberration is insufficiently corrected, and it is difficult to achieve both lateral chromatic aberration correction. If the lower limit of the expression (10) is exceeded, the refractive power of the positive lens will increase, and higher-order halo and coma will increase, making it difficult to achieve good optical performance. More preferably, conditional expression (10) should be set as follows.
1.88 <n1p <2.20 (10a)

Next, the features of the lens configuration of each example will be described.
A specific lens configuration according to the first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a lens cross-sectional view of an imaging lens of Example 1 (Numerical Example 1) of the present invention. The imaging lens of Example 1 (Numerical Example 1) includes, in order from the object side, a first lens group G1, an aperture stop SP, and a second lens group G2 having a positive refractive power. The first lens group G1 includes, in order from the object side, negative meniscus lenses L1 and L2 and a positive lens L3 that are convex on the object side. The second lens group G2 includes, in order from the object side, a cemented lens in which a negative lens L4 and a positive lens L5 are cemented, a positive lens L6, and a positive lens L7. The positive lenses L5 and L6 are made of glass having anomalous dispersion, and the positive lenses L5 and L6 are made of materials that satisfy the conditional expressions (d), (e), (f), and (g). It is configured as a positive lens .

  FL is a parallel plate corresponding to a low-pass filter, an IR cut filter, or the like. Reference numeral I denotes an image pickup surface, which corresponds to an image pickup surface such as a solid-state image pickup device (photoelectric conversion device) that receives and photoelectrically converts an image formed by a lens. The material of the lens barrel member that regulates the distance between the lenses and the back focus is aluminum.

  Table 1 shows the corresponding values of Example 1 for the conditional expressions (1) to (10). Numerical Example 1 satisfies all the conditional expressions, and realizes an imaging lens in which a small and light weight, a wide angle, a bright F number, chromatic aberration are corrected well, and a change in imaging position due to temperature is suppressed. .

FIG. 3 is a lens cross-sectional view of the imaging lens of Example 2 (Numerical Example 2) of the present invention. The lens configuration is exactly the same as in Example 1. Note that L5 uses a glass having anomalous dispersion, and L5 is configured as a positive lens using a material that satisfies the conditional expressions (d), (e), (f), and (g) .

  The material of the lens barrel member that regulates the distance between the lenses and the back focus is aluminum. Table 1 shows the corresponding values of Example 2 for the conditional expressions (1) to (10). Numerical Example 2 satisfies all the conditional expressions, and realizes an imaging lens in which a small size, light weight, wide angle, bright F-number, chromatic aberration are well corrected, and a change in imaging position due to temperature is suppressed. .

FIG. 5 is a lens cross-sectional view of the imaging lens of Example 3 (Numerical Example 3) of the present invention. The lens configuration is exactly the same as in Example 1. Note that L5 and L6 are made of glass having anomalous dispersion, and L5 and L6 are configured as positive lenses using a material that satisfies the conditional expressions (d), (e), (f), and (g). doing.

  The material of the lens barrel member that regulates the distance between the lenses and the back focus is aluminum. Table 1 shows the corresponding values of Example 3 for the conditional expressions (1) to (10). Numerical Example 3 satisfies all the conditional expressions, and realizes an imaging lens in which a small and light weight, a wide angle, a bright F number, chromatic aberration are corrected well, and a change in imaging position due to temperature is suppressed. .

FIG. 7 is a lens cross-sectional view of the imaging lens of Example 4 (Numerical Example 4) of the present invention. The imaging lens of Example 4 includes, in order from the object side, a first lens group G1, an aperture stop SP, and a second lens group G2 having a positive refractive power. The first lens group G1 includes, in order from the object side, negative meniscus lenses L1 and L2 and a positive lens L3 that are convex on the object side. The second lens group G2 includes, in order from the object side, a cemented lens in which a positive lens L4 and a negative lens L5 are cemented, and a positive lens L6 having an aspheric surface. The positive lens L4 uses a glass having anomalous dispersion, and the positive lens L4 is configured as a positive lens using a material that satisfies the conditional expressions (d), (e), (f), and (g). doing.

  FL is a parallel plate corresponding to a low-pass filter, an IR cut filter, or the like. Reference numeral I denotes an image pickup surface, which corresponds to an image pickup surface such as a solid-state image pickup device (photoelectric conversion device) that receives and photoelectrically converts an image formed by a lens. The material of the lens barrel member that regulates the distance between the lenses and the back focus is aluminum.

  Table 1 shows corresponding values of Example 4 for the conditional expressions (1) to (10). Numerical Example 4 satisfies all the conditional expressions, and realizes an imaging lens in which a small and light weight, a wide angle, a bright F number, chromatic aberration are corrected well, and a change in imaging position due to temperature is suppressed. .

FIG. 9 is a lens cross-sectional view of the imaging lens of Example 5 (Numerical Example 5) of the present invention. The lens configuration is exactly the same as in Example 4. L4 and L6 are made of glass having anomalous dispersion, and L4 and L6 are configured as positive lenses using materials that satisfy the conditional expressions (d), (e), (f), and (g). ing.
The material of the lens barrel member that regulates the distance between the lenses and the back focus is aluminum.

Table 1 shows the corresponding values of Example 5 for the conditional expressions (1) to (10). Numerical Example 5 satisfies all the conditional expressions, and realizes an imaging lens in which a small and light weight, a wide angle, a bright F number, chromatic aberration are corrected well, and a change in imaging position due to temperature is suppressed. .

  FIG. 11 is a schematic diagram of a main part of the imaging apparatus 110. In FIG. 11, reference numeral 101 denotes an imaging lens according to any of the first to fifth embodiments, 102 denotes a first lens group, 103 denotes a second lens group, and SP denotes an aperture stop. Reference numeral 109 denotes an imaging unit including an imaging element and the like.

  Reference numeral 108 denotes a motor (driving means) that electrically drives the aperture stop SP. Reference numeral 107 denotes a detector such as an encoder, a potentiometer, or a photosensor for detecting the aperture diameter of the aperture stop SP. Reference numeral 104 denotes a glass block corresponding to a low-pass filter, an IR cut filter, or the like in the camera 109. Reference numeral 105 denotes a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that receives an object image formed by the single focus lens 101. is there. Reference numeral 106 denotes a CPU that controls various types of driving of the imaging lens 101, image processing calculations, and the like.

Thus, by applying the imaging lens of the present invention to an imaging camera or the like, an imaging device having high optical performance is realized.
The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

  Numerical examples 1 to 5 for Examples 1 to 5 of the present invention are shown below. In each numerical example, the surface number indicates the order of the surfaces from the object side, r is the radius of curvature, d is the lens thickness or surface interval, and nd and νd are the refractive index and Abbe number of the optical member. Aspherical surfaces are marked with * next to the surface number.

The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, k is the cone constant, A4, A6, A8, A10, A12. When each of them is an aspheric coefficient, it is expressed by Equation 1. “E-Z” means “× 10 ^−Z ”.

Numerical example 1
Unit mm

Surface data surface number rd nd vd Effective diameter
1 9.506 0.80 1.80 400 46.6 10.60
2 4.605 1.06 7.94
3 * 5.351 0.80 1.58313 59.4 7.71
4 * 2.411 5.32 6.00
5 44.521 1.72 2.00069 25.5 4.45
6 -11.719 2.47 4.02
7 (Aperture) ∞ 1.87 3.67
8 23.066 0.80 1.95906 17.5 3.59
9 5.578 3.43 1.55332 71.7 3.49
10 -8.933 0.15 5.40
11 20.695 1.63 1.49700 81.5 5.98
12 -30.189 0.09 6.43
13 9.814 1.89 1.77250 49.6 6.81
14 184.683 3.99 6.69
15 ∞ 0.50 1.51633 64.1 10.00
16 ∞ 0.50 10.00
Image plane ∞

Aspheric data 3rd surface
K = -1.04978e + 000 A 4 = 1.81276e-003 A 6 = -2.22766e-004 A 8 = 1.40361e-005 A10 = -5.52816e-007 A12 = 1.00402e-008

4th page
K = -9.51025e-001 A 4 = 5.11349e-003 A 6 = -4.40018e-004 A 8 = 3.54637e-005 A10 = -3.15904e-006 A12 = 1.08491e-007

Various data focal length 2.90
F number 1.854
Half angle of view 48.98
Statue height 3.00
Total lens length 26.86
BF 4.99

Entrance pupil position 4.94
Exit pupil position -36.27
Front principal point position 7.61
Rear principal point position -2.40

Lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 32.59 9.71 23.19 43.94
2 7 6.70 9.86 5.50 -1.28
3 15 ∞ 0.50 0.16 -0.16

Single lens Data lens Start surface Focal length
1 1 -11.98
2 3 -8.36
3 5 9.41
4 8 -7.85
5 9 6.78
6 11 24.97
7 13 13.35
8 15 0.00

Numerical example 2
Unit mm

Surface data surface number rd nd vd Effective diameter
1 10.866 0.80 1.72916 54.7 10.84
2 4.803 1.11 8.12
3 * 5.693 0.80 1.55332 71.7 7.89
4 * 2.442 5.21 6.15
5 35.650 1.87 1.90366 31.3 4.91
6 -10.719 2.79 4.49
7 (Aperture) ∞ 1.98 3.71
8 29.399 0.80 1.92286 18.9 3.60
9 5.765 2.82 1.55332 71.7 3.67
10 -9.831 0.15 5.18
11 24.395 1.69 1.51633 64.1 5.71
12 -22.065 0.10 6.23
13 9.534 1.91 1.77250 49.6 6.66
14 132.428 3.99 6.55
15 ∞ 0.50 1.51633 64.1 10.00
16 ∞ 0.50 10.00
Image plane ∞

Aspheric data 3rd surface
K = -9.49449e-001 A 4 = 1.49704e-003 A 6 = -1.99514e-004 A 8 = 1.10616e-005 A10 = -3.91278e-007 A12 = 6.43519e-009

4th page
K = -9.17463e-001 A 4 = 4.58466e-003 A 6 = -4.11385e-004 A 8 = 3.09367e-005 A10 = -2.81263e-006 A12 = 9.70174e-008

Various data focal length 3.00
F number 1.85
Half angle of view 48.01
Statue height 3.00
Total lens length 26.87
BF 4.99

Entrance pupil position 5.07
Exit pupil position -29.37
Front principal point position 7.77
Rear principal point position -2.50

Lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 27.64 9.80 20.25 36.47
2 7 6.82 9.45 5.30 -1.26
3 15 ∞ 0.50 0.16 -0.16

Single lens Data lens Start surface Focal length
1 1 -12.50
2 3 -8.47
3 5 9.30
4 8 -7.90
5 9 7.02
6 11 22.72
7 13 13.21
8 15 0.00

Numerical Example 3
Unit mm

Surface data surface number rd nd vd Effective diameter
1 9.748 0.80 1.77250 49.6 11.17
2 5.255 1.19 8.70
3 * 5.981 0.80 1.69350 53.2 8.43
4 * 2.585 5.11 6.48
5 28.630 1.70 2.00100 29.1 5.24
6 -13.722 2.80 4.84
7 (Aperture) ∞ 2.47 4.74
8 22.518 0.80 1.95906 17.5 4.65
9 6.223 2.66 1.49700 81.5 4.52
10 -9.380 0.10 5.91
11 28.102 1.53 1.49700 81.5 6.58
12 -23.071 0.05 7.06
13 8.429 2.14 1.77250 49.6 7.71
14 376.608 3.97 7.50
15 ∞ 0.50 1.51633 64.1 10.00
16 ∞ 0.50 10.00
Image plane ∞

Aspheric data 3rd surface
K = -1.32242e + 000 A 4 = 5.20488e-004 A 6 = -1.48931e-004 A 8 = 1.11905e-005 A10 = -4.18229e-007 A12 = 6.39074e-009

4th page
K = -9.99466e-001 A 4 = 3.58264e-003 A 6 = -4.74680e-004 A 8 = 4.62609e-005 A10 = -2.61091e-006 A12 = 5.95543e-008

Various data focal length 3.00
F number 1.44
Half angle of view 48.02
Statue height 3.00
Total lens length 26.96
BF 4.97

Entrance pupil position 5.28
Exit pupil position -48.59
Front principal point position 8.10
Rear principal point position -2.50

Lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 45.11 9.61 29.49 55.08
2 7 6.53 9.75 5.67 -1.30
3 15 ∞ 0.50 0.16 -0.16

Single lens Data lens Start surface Focal length
1 1 -16.00
2 3 -7.27
3 5 9.46
4 8 -9.19
5 9 7.98
6 11 25.75
7 13 11.13
8 15 0.00

Numerical Example 4
Unit mm

Surface data surface number rd nd vd Effective diameter
1 13.048 0.80 1.72916 54.7 13.50
2 5.418 2.52 9.58
3 * 6.750 0.80 1.55332 71.7 8.68
4 * 2.058 2.98 6.35
5 19.995 4.45 2.00069 25.5 5.88
6 -18.928 2.24 4.22
7 (Aperture) ∞ 1.51 2.82
8 12.487 2.34 1.55332 71.7 3.36
9 -3.752 0.80 1.92286 18.9 4.24
10 -8.215 0.10 4.99
11 * 29.915 2.89 1.58313 59.4 5.33
12 * -3.987 3.90 6.35
13 ∞ 0.50 1.51633 64.1 10.00
14 ∞ 0.50 10.00
Image plane ∞

Aspheric data 3rd surface
K = -1.94531e + 000 A 4 = -3.09257e-004 A 6 = -1.06411e-004 A 8 = 7.59464e-006 A10 = -2.37906e-007 A12 = 3.10972e-009

4th page
K = -9.58691e-001 A 4 = 2.22709e-004 A 6 = -3.93665e-004 A 8 = 1.76771e-005 A10 = -3.48121e-007 A12 = 1.37046e-008

11th page
K = -1.10719e + 002 A 4 = -2.05379e-003 A 6 = -8.73467e-005 A 8 = 1.10319e-006 A10 = -1.01202e-006 A12 = 6.39237e-009

12th page
K = -3.25120e + 000 A 4 = -3.44869e-003 A 6 = 4.42330e-005 A 8 = 3.41073e-006 A10 = -9.32801e-007 A12 = 1.92139e-008

Various data focal length 2.00
F number 1.85
Half angle of view 59.91
Statue height 3.00
Total lens length 26.14
BF 4.90

Entrance pupil position 5.17
Exit pupil position -100.03
Front principal point position 7.13
Rear principal point position -1.50

Lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 -16.62 11.54 -4.98 -23.87
2 7 5.11 7.63 4.85 -1.00
3 13 ∞ 0.50 0.16 -0.16

Single lens Data lens Start surface Focal length
1 1 -13.30
2 3 -5.70
3 5 10.31
4 8 5.50
5 9 -8.19
6 11 6.23
7 13 0.00

Numerical Example 5
Unit mm

Surface data surface number rd nd vd Effective diameter
1 12.783 0.80 1.77250 49.6 13.50
2 5.451 2.19 9.64
3 * 6.519 0.80 1.55332 71.7 9.00
4 * 2.139 4.69 6.57
5 18.835 3.22 1.95906 17.5 5.10
6 -44.018 1.89 3.80
7 (Aperture) ∞ 0.71 4.06
8 8.237 3.40 1.43875 94.9 4.19
9 -4.044 0.80 1.95906 17.5 4.37
10 -7.680 0.53 5.10
11 * 9.309 3.13 1.55332 71.7 6.19
12 * -4.944 3.90 6.37
13 ∞ 0.50 1.51633 64.1 10.00
14 ∞ 0.50 10.00
Image plane ∞

Aspheric data 3rd surface
K = -2.13664e + 000 A 4 = -1.03063e-004 A 6 = -1.07352e-004 A 8 = 7.73577e-006 A10 = -2.29290e-007 A12 = 2.97657e-009

4th page
K = -9.60291e-001 A 4 = 2.24345e-004 A 6 = -3.85137e-004 A 8 = 2.07413e-005 A10 = -4.35811e-007 A12 = 2.73398e-008

11th page
K = -2.31297e + 000 A 4 = -3.55059e-004 A 6 = 2.80314e-005 A 8 = 6.45316e-006 A10 = -1.04930e-007 A12 = 1.40978e-009

12th page
K = -4.62509e + 000 A 4 = -1.10781e-003 A 6 = 1.05266e-004 A 8 = 4.66334e-006 A10 = -4.58068e-007 A12 = 4.11357e-008

Various data focal length 2.00
F number 1.44
Half angle of view 59.91
Statue height 3.00
Total lens length 26.88
BF 4.90

Entrance pupil position 5.06
Exit pupil position -83.03
Front principal point 7.01
Rear principal point position -1.50

Lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 -10.81 11.70 -1.94 -17.96
2 7 5.60 8.56 5.22 -1.91
3 13 ∞ 0.50 0.16 -0.16

Single lens Data lens Start surface Focal length
1 1 -12.92
2 3 -6.15
3 5 14.11
4 8 6.75
5 9 -9.98
6 11 6.33
7 13 0.00

L1 first lens, L2 second lens, L3 third lens, L4 fourth lens, L5 fifth lens, L6 sixth lens, L7 seventh lens, G1 first lens group, G2 second lens group, SP aperture stop I Image plane

Claims (8)

A single-focus imaging lens that is arranged in order from the object side to the image side, and includes a first lens group, an aperture stop, and a second lens group having a positive refractive power,
Wherein the first lens group, disposed in order from the object side to the image side, a negative meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface on the object side, and a positive lens,
The second lens group includes a negative lens and two or more positive lenses,
When the refractive index based on the d-line of the lens material included in the second lens group is N2a, the Abbe number is ν2a, the partial dispersion ratio is θ2a, and the amount of change in the refractive index with respect to temperature change is dn2a / dT The second lens group is
62 <ν2a
N2a <1.63
0.605− (ν2a / 1000) <θ2a
dn2a / dT <−2.4 × 10 ⁻⁶
A positive lens that satisfies the conditional expression
F is the focal length of the entire system, f2a is the focal length when there is one positive lens that satisfies all the conditional expressions included in the second lens group, and f2a when there are two or more positive lenses. When the total length of the photographing lens is TD and the back focus of the photographing lens is BF,
0.20 <f / f2a <0.80
3.00 <TD / BF <6.50
Satisfying the conditional expression
When the focal length of the first lens group f1, the refractive index relative to the d line of the material of said positive lens in the first lens group and N1P,
-0.21 <f / f1 <0.25
1.88 <n1p <2.40
A photographic lens characterized by satisfying the following conditional expression: When the focal length of the front Stories second lens group and the f2,
0.20 <f / f2 <0.70
The photographic lens according to claim 1, wherein the following conditional expression is satisfied. When said ν2p an average Abbe number of materials of the positive lens in the second lens group, Nyu2n the average Abbe number of the negative lens material contained in the second lens group,
2.00 <ν2p / ν2n <6.00
The photographic lens according to claim 1, wherein the following conditional expression is satisfied. The second lens group includes a cemented lens in which a negative lens and a positive lens are cemented. The refractive index of the material of the negative lens constituting the cemented lens is ncn, and the refraction of the material of the positive lens that configures the cemented lens. When the rate is ncp,
0.20 <ncn-ncp <0.60
The photographing lens according to claim 1, wherein the following conditional expression is satisfied. When said ν1p the Abbe number of the material of the positive lens in the first lens group, Nyu1n the average Abbe number of materials of the negative lenses included in the first lens group,
0.20 <ν1p / ν1n <0.70
Photographing lens according to any one of claims 1 to 4, characterized by satisfying the conditional expression. A photographing lens according to any one of claims 1 to 5, an imaging apparatus characterized by having an imaging element for receiving an image formed by the imaging lens. It further has a lens barrel member that regulates the back focus of the photographing lens, and when the linear expansion coefficient of the material of the lens barrel member is α,
The imaging apparatus according to claim 6 , wherein a conditional expression of 1.50 × 10 ⁻⁵ <α <2.50 × 10 ⁻⁵ is satisfied. When the maximum image height in the image sensor is Y, and the F number of the photographing lens when focusing on infinity is Fno,
0.40 <f ² /(Y×Fno)<3.00 (unit: mm)
The imaging apparatus according to claim 6 or 7, characterized in that to satisfy the condition.

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